These two images, taken about a week apart by NASA's Hubble Space Telescope, show four moons orbiting the distant, icy dwarf planet Pluto.

Nix is the inner of the two moons discovered orbiting Pluto in 2005. Nix and Hydra are roughly 5,000 times fainter than Pluto and are about two to three times farther from Pluto than its large moon, Charon, which was discovered in 1978. Nix and Hydra are roughly 20 to 70 miles (32 to 113 km) wide.

They are so small and so faint that scientists combined a short exposure of Pluto and Charon and a long exposure of Nix and Hydra to create images of them all together.

Discovery:
Nix was discovered in June, 2005 by Hal Weaver and a large team of astronomers using the Hubble Space Telescope.

How Nix Got its Name:
Nix was named for the Greek goddess of darkness and night and mother of Charon.